Dishwasher with a pre-conditioning steam cycle

ABSTRACT

A dishwasher is provided that performs a pre-conditioning steam cycle. The dishwasher includes a washing compartment for receiving dishware to be subjected to a dishwashing program and a wash water assembly for introducing a selected one of wash water and rinse water into the washing compartment. The wash water assembly is controllable to perform a wash/rinse/dry program and a rinse and hold program. The dishwasher also includes a vapor generator assembly for introducing steam vapor into the washing compartment and a control arrangement for controlling the vapor generator assembly to perform a rinse and hold cycle wherein steam vapor is introduced into the washing compartment at selected intervals.

BACKGROUND OF THE INVENTION

The present invention is directed to a dishwasher having apre-conditioning steam cycle in which steam is introduced at selectedintervals.

According to U.S. Pat. No. 4,106,517, dishwashers have been offeredhaving dishwasher control systems that utilize a selector switch withindividually operated switches controlled manually by pushbuttons, suchas “pots and pans”, “normal soil”, “quick wash”, “rinse and hold”, and“rinse and dry”, together with a cancel button. In such systems, theuser initiates a cycle by pushing a selected button down beyond alatching position to a momentary position until the machine starts,after which the button is released and the machine automaticallyfinishes the cycle. A Rinse and Hold cycle may be desired if items willbe sitting longer than a day in the dishwasher before a full load canaccumulate. This minimizes food odor. A version of a Rinse and Holdcycle is a so-called “half-load” cycle. Rinse and hold cycles are oftenemployed to wash lightly soiled items when a quick turnaround is needed.

According to U.S. Pat. No. 7,104,269, the conventional heating elementof a dishwasher (located in the recirculating sump) must raise thetemperature of not only the 1.5-3.0 gallons of water that is used in agiven cycle (equivalent to 12-24 lbs. of water), but also must raise thetemperature of the kitchenware to be cleaned, including dishes, pots,pans, silverware and like kitchen utensils (about 20 lbs.), and thecavity/rack/spray-on system of the dishwashing cavity (about another 20lbs.). The power supply must not only feed the heating element, but alsoperform the non-heating functions of the dishwasher—e.g., driving thepump that circulates the water under pressure into and around thecavity, driving the controls of the consumer interface, and the like.Furthermore, according to U.S. Pat. No. 7,104,269, separate and apartfrom the constraint imposed on a US residential dishwasher by thelimited power supply available, there is also a constraint on the sizeor volume of a US residential dishwasher. Both builder-supplieddishwashers (for new home construction) and replacement dishwashers areexpected to fit within a given volume of “counter space,” which hasbecome standardized over time to provide a dishwasher cavity of about 7cubic feet. The standard volume evolved in a way that allowed thedishwasher to fit under a counter at the standard kitchen counterheight, with a door at a height at which consumers felt comfortableloading dishes, and a combined height and width that did not take up toomuch “cupboard” space yet held a reasonable number of dishes. Takinginto account the height of the lower tray rollers, the thickness of thedoor itself, and the space between the bottom of the lower tray and thebottom of the dishwasher cavity leaves approximately 9 inches betweenthe floor and the bottom of the dishwashing cavity. All the workingparts of the dishwasher (e.g., inlet water connection, electrical powerconnection, inlet water valve, motor, valves, hoses, controls, etc.)must fit within this limited height external of the dishwashing cavity.

Thus, there is a need for improvements in dishwashers which enhance theenergy saving capability of a dishwasher yet do not compel an expansionof the outer dimension of the dishwasher to a degree that the dishwasherwill no longer fit within the existing industry standard for “cupboardspace.”

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided adishwasher that performs a pre-conditioning steam cycle. The dishwasherincludes a washing compartment for receiving dishware to be subjected toa dishwashing program and a wash water assembly for introducing aselected one of wash water and rinse water into the washing compartment.The wash water assembly is controllable to perform a wash/rinse/dryprogram and a rinse and hold program. The dishwasher also includes avapor generator assembly for introducing steam vapor into the washingcompartment and a control arrangement for controlling the vaporgenerator assembly to perform a steam and hold cycle wherein steam vaporis introduced into the washing compartment at selected intervals.

According to a further feature of the one aspect of the presentinvention, the control arrangement controls the vapor generator assemblyto perform a steam and hold cycle in lieu of a rinse and hold cycle.

According to another feature of the one aspect of the present invention,the control arrangement controls the vapor generator assembly to performa modified rinse and hold cycle in coordination with a steam and holdcycle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view, in partial section, of a dishwasherhaving one embodiment of the vapor generator assembly of the presentinvention;

FIG. 2 is an enlarged schematic view of the vapor generator assemblyshown in FIG. 1; and

FIG. 3 is a schematic view of the touchpad and control arrangement ofthe dishwasher shown in FIGS. 1 and 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As illustrated in FIGS. 1-3, one embodiment of the dishwasher of thepresent invention is illustrated and is generally denominated as thedishwasher 10. The dishwasher 10 includes an outside facade housing 12delimiting an interior space in which is located a dishware handlingcontainer 14. The dishware handling container 14 delimits a washingvolume 16. A sump portion 18 is formed at the bottom of the washingvolume 16. A central inlet 20 extends upwardly from the sump portion 18.

A spray arm 22 is mounted on the central inlet 20 in a manner such thatthe spray arm 22 can rotate relative to the central inlet 20 about avertical axis. A plurality of spray outlets 24 are formed in the topsurface of the respective left and right hand wings of the spray arm 22.

A wash pump 26 located below the sump portion 18 includes a wash pumpmotor serving as a drive motor, an impeller driven by the wash pumpmotor, and a housing enclosing the impeller. The housing of the washpump 26 has an inlet port 28 communicated with the base of the sumpportion 18 and an outlet port 30 communicated with a lower end of thecentral inlet 20. The central inlet 20 has an upper opening communicatedwith the spray arm 22.

A drain pump 32 is located below the sump portion 18. A stock heater 34is operably connected to the sump portion 18 for heating fluids such aswash solution or rinse solution that is collected in the sump portion18. A drain conduit 36 extends from the drain pump 32 to a draintake-off location exteriorly of the dishwasher. A water supply valve 38,a drying fan 40, a drying air intake duct 42, and an exhaust duct 44 areall located exteriorly of the dishware handling container 14.

An upper dishware rack 46 is mounted in an upper region of the dishwarehandling container 14 on a pair of roller track assemblies that permitthe upper dishware rack 46 to be selectively withdrawn out of thedishware handling container 14 and retracted into the dishware handlingcontainer 14. A lower dishware rack 48 is mounted lower region of thedishware handling container 14 on a pair of roller track assemblies thatpermit the lower dishware rack 48 to be selectively withdrawn out of thedishware handling container 14 and retracted into the dishware handlingcontainer 14. The outside facade housing 12 has a front access opening50 through which the racks 46, 48 can be extended and retracted. A door52 is hingedly mounted to the outside facade housing 12 and movablebetween positions in which it respectively closes off, and permitsaccess to, the opening 50. A control device 54 is mounted in the outsidefacade housing 12 below the door 52 and is operably connected to adisplay panel (not shown) on the front of the outside facade housing 12.

The vapor generator 110 includes a boiler 112, a heating element 114, adischarge member 116, a sprayer 118, and a housing 120. The boiler 112is disposed within the housing 120 of the vapor generator 110. Theheating element 114, which may be integral with or positioned inside theboiler 112, is preferably an electrical coil that radiates heat whenenergized. The electrical coil of the heating element 114 is anelectrical resistance heater that heats up in response to the flow of anelectrical current therethrough, whereupon the heating element 114, uponreaching a predetermined temperature, vaporizes water in the boiler 112into a vapor such as steam. The discharge member 116 is provided on theboiler 112 to control the release of the steam or steam/liquid mixture(hereinafter “steam”). The discharge member 116 may be configured as topermit a timed release of steam from the vapor generator 110 or topermit release of steam from the vapor generator 110 in response to apredetermined event. For example, the discharge member 116 can beconfigured as a one-way biased valve (not shown) having a spring member,a ball member, and a seat. By adjusting the spring constant of thespring member, a pre-determined amount of pressure can be induced withinthe boiler 112. When this pre-determined pressure is reached, the ballmember lifts off the seat and releases the steam. Alternatively, thedischarge member 116 may be a bore or passage (not shown) having apredetermined diameter that is selected to induce a predeterminedpressure in the boiler 112.

The sprayer 118 sprays fluid in a pre-determined manner (e.g., velocity,spray pattern, volume, duration, degree of aeration) into the dishwarehandling container 14. The sprayer 118 may be configured to atomize(i.e., create a fine mist), pressurize, disperse the steam vapor orotherwise form a pre-determined flow pattern for the steam vapor. Theresidential “dwell” time of the steam vapor on the surface of thedishware in the dishware handling container 14 dislodges or otherwisepromotes the dislodgement of materials such as contaminants or foodparticles on the surface of the dishware. This effect may provide afinal desired level of cleanliness or some intermediate level ofcleanliness.

The vapor generator 110 is also preferably provided with control andsensing features to permit an optimum reliable operation. In thisregard, the vapor generator 10 includes safety sensors 122, an interlock124, a timer 126, and a microprocessor 128. The timer 126 controls thevapor generator 110 operation by, for example, energizing the heatingcoil 114 for a preset duration. The safety sensors 122 can monitorparameters such as pressure, temperature, electrical flow, moisture andwater level. In an advantageous arrangement, the safety sensors 122 areoperably coupled to the interlock 124 such that vapor generator 110operation is interrupted or terminated upon detection of apre-determined condition. The pre-determined condition can includeexcessive pressure or temperature, a fluid leak, an electrical short orother event that can compromise the operation of the vapor generator 110or cause damage or injury. Optionally, the microprocessor 128 can beprogrammed to cycle the vapor generator 110 through the cleaningoperation and to alter operation in the event an undesirable conditionis detected.

Upon activation, the heating coil of the heating element 114 boils thewater in the boiler 112 to create steam. This steam is brought to apre-determined condition (e.g., pressure) by the discharge member 116.The steam released from the boiler 112 flows through the sprayer 118. Inthe event that additional water needs to be supplied, this water issupplied via an inlet 130 leading into the boiler 112.

The operation of dishwasher 10 is as follows. A user loads the dishware,which may be comprised, for example, of plates, saucers, glasses, cups,pots, or pans as well as cutlery such as spoons, forks, and knives, intoa selected one, or both, of the upper dishware rack 46 and the lowerdishware rack 48. Each respective dishware rack can be withdrawnoutwardly of the dishware handling container 14 to facilitate loading ofthe soiled dishware into the rack and thereafter the rack can beretracted into the dishware handling container 14. The door 52 is movedto its respective position in which it closes off the front accessopening 50 once the upper dishware rack 46 and/or the lower dishwarerack 48 has been loaded with soiled dishware.

With soiled dishware now loaded into the dishwasher 10, the user canselect from one of a range of operating programs to commence or delaythe operation of the dishwasher 10. In this regard, the user chooses anoperating program for the dishwasher by inputting a program selectionvia a touchpad 200 on the display panel. The touchpad 200, which isschematically shown in FIG. 3, is operatively connected to a controlinterface 202 which may be, for example, in the form of an ASICsemiconductor chip. One of the programs that is available to be selectedby the user is a wash/rinse/dry cycle, generally indicated aswash/rinse/dry cycle 204 in FIG. 3. The selection of the wash/rinse/drycycle 204 causes the dishwasher 10 to first perform a dishware washingsub-program, wherein water is supplied into the sump portion 18 via thewater supply valve 38, the stock heater 34 is operated to heat the fillwater that has been supplied into the sump portion 18, and the wash pump26 is operated to pump the now heated fill water from the sump portion18 through the outlet port 30 into the central inlet 20, with the heatedwater thereafter exiting the nozzles in the spray arm 22 into thewashing volume 16. The motive action of the water flowing through thespray arm 22 effects rotation of the spray arm 22 and the soileddishware retained in the racks 46, 48 are thereby wetted by the watersprayed by the spray arm 22. Water on the soiled dishware drainsdownwardly, thereby effecting removal of the food debris on the soileddishware, and this downwardly flowing water ultimately is collected inthe sump portion 18. The drain pump 32 is operated at a predeterminedfrequency, or at a responsive frequency responsive to the collection ofwater in the sump portion 18, to pump the water collected in the sumpportion 18 through the drain conduit 36 to the drain take-off location.

During the rinse sub-program of the wash/rinse/dry program 204, freshfill water is introduced into the sump portion 18 and is pumped via thewash pump 26 to be sprayed by the spray arm 22 against the dishwareretained in the racks 46, 48, which should now be largely free of fooddebris. The rinse water drains to the sump portion 18 and can befiltered to remove entrained food debris via a conventional filterarrangement and then recirculated again into contact with the dishware.At the conclusion of the rinse sub-program, the drying fan 40 isoperated to direct heated air into the dishware handling container 14and spent drying is exhausted via the exhaust duct 44.

The touchpad 200 also permits a user to choose other programs inaddition to the wash/rinse/dry program 204. For example, the user canselect a “rinse and hold” program 206, whereupon, in connection withthis program, a predetermined amount of fill water is introduced intothe sump portion 18 and ultimately sprayed via the spray arm 22 into thedishware handling compartment 14 to effect wetting of the soileddishware. This introduced amount of fill water in the “rinse and hold”program 206 is a lesser amount than the water introduced during the washsub-program of the wash/rinse/dry program 204 and the purpose of thewater introduced in the “rinse and hold” 206 is to effect wetting of thesoiled dishware to prevent food debris on the dishware from “caking” orsticking in a tenacious manner to the surface of the dishware for aperiod of time between the loading of the soiled dishware into thedishwasher 10 and a later time, which may be several hours later, atwhich awash/rinse/dry program 204 is initially commenced.

The touchpad 200 also offers the possibility for the user to select a“steam and hold” program 208 in lieu of, for example, either thewash/rinse/dry cycle 204 or the “rinse and hold” program 206. The steamand hold program 208 is a program that introduces steam into thedishware handling container 14 in a predetermined manner to accomplishthe same objective as the “rinse and hold” program 206—namely, toaccomplish the objective of wetting the soiled dishware to a degree thatinhibits the “caking” or tenacious sticking of food debris to thesurface of the dishware until a wash/rinse/dry program 204 is ultimatelyperformed. The steam and hold program 208 advantageously offers thebenefit that a fair amount of water can be conserved in contrast to thewater introduced during the rinse and hold program 206 and, moreover,offers the benefit of energy savings in that the energy required togenerate steam for the steam and hold program 208 can, in manycircumstances, lead to an ultimate energy savings in that less heatenergy is needed during the subsequent wash/rinse/dry program 204.

Upon selection of the steam and hold program 208, the control interface202 controls the vapor generator 110 to cause energization of theheating element 114 within the boiler 112. This energization of theelement 114 results in a heating up of water in the boiler 112 to adegree that water is vaporized into steam in a completely gaseous formor in a gas/liquid form, both forms being collectively referred to as“steam vapor.” The steam vapor is released by the discharge member 116into the dishware handling compartment 114 and the steam vapor contactsthe food debris on the soiled dishware and promotes dislodgement of thefood debris from the surface of the dishware. The contact of the steamvapor with the food debris and the surfaces of the dishware, as well asthe surfaces on the interior of the dishware handling compartment 14,causes condensation of the steam vapor and the resulting condensed waterdroplets ultimately flow downwardly and are collected within the sumpportion 18.

The cyclic frequency at which steam vapor is introduced by the dischargemember 116 into the dishware handling compartment 14 can be configuredaccording to a pre-selected frequency or, alternatively, in response toa real-time evaluated condition. With respect to introducing steam vaporin accordance with a pre-selected frequency, steam vapor may beintroduced, for example, every 30 minutes until a maximum pre-set numberof steam introductions had been performed or, alternatively, until awash/rinse.dry program 204 has commenced operation. Thus, a total ofeight introductions of steam vapor may be performed within a four hourperiod with such steam vapor being introduced during each 30 minuteinterval and thereafter no additional steam vapor being introduced. Itcan thus be understood that, for example, during an overnight period ofseveral hours, the introduction of steam vapor according to thejust-described steam vapor introduction frequency will beneficiallyresult in a continuous level of moisture or a cyclically refreshed levelof moisture in the dishware handing compartment 14 that beneficially atleast largely inhibits the “caking” or tenacious sticking of food debristo the surfaces of the dishware and optimally contributes to adetachment of food debris from dishware before another dishwasheroperation has commenced.

A plurality of pre-set steam vapor frequency programs can be stored, forexample, in a frequency program 210 that can be accessed when the steamand hold 208 is selected, with the user having the capability to selecta given one of the pre-set steam vapor frequencies via the touchpad 200.Alternatively, the steam and hold program 208 can be controlled via theinputs provided through the touchpad 200 to perform introduction ofsteam vapor in response to a real-time condition. As seen in FIG. 3, asensing response program 212 is operatively connected to the controlarrangement 202 and can be accessed by the steam and hold program 208.The sensing response program 212 may control and receive informationfrom components such as a turbidity sensor (not shown) that senses alevel of turbidity in the dishware handling compartment 14 or thesensing response program 212 may control and receive information from asensor operatively connected to a filter (not shown) in the sump portion18 that senses the level of solids buildup on the filter. In response toinformation provided by the sensing response program 212, the steam andhold program 208 can regulate the frequency at which steam vapor isintroduced into the dishware handling compartment 14 and consequentlyincrease, decrease, or cease the introduction of steam vapor in responseto a chosen sensed parameter such as, for example, the sensed turbidityor the sensed solids buildup. Moreover, the control arrangement 202 canbe provided, for example, with empirical data reflecting known orestimated turbidity or solids buildup values and these known values canbe compared to, or correlated with, the sensed corresponding turbidityor solid buildup values such that the steam and hold program 208 causes,for example, cessation of further introductions of steam vapor once acomparison of a known turbidity value with a sensed turbidity revealsthat the two values are the same.

The control arrangement 202 also controls a hybrid program 214 thatpermits both the benefits of a “rinse and hold” program and of a “steamand hold” program to be obtained. The hybrid program 214 causes anintroduction of water from the sump portion 18 in the same quantity andmanner as the water distribution step performed during the rinse andhold program 206 and causes, as well, an introduction of steam vaporfrom the vapor generator 110. Thus, soiled dishware in the dishwarehandling compartment 14 can be subjected to both a completely liquidspray from the spray arm 22 during a rinse and hold step and subjectedto steam vapor from the vapor generator 110 during a steam and hold stepand this hybrid or combined treatment can beneficially result inenhanced removal of food debris from soiled dishware. It can beappreciated that the steam and hold program 208 and the hybrid program214 can result in an ultimate water and energy saving process ascompared to a conventional process.

While a particular embodiment of this invention has been shown anddescribed in connection with a dishwasher having a pre-conditioningsteam cycle in which steam is introduced at selected intervals, this isby way of illustration only and does not constitute any sort oflimitation since there are various alterations, changes, deviations,amendments, revisions, eliminations, additions, substitutions, omissionsand departures which may be made in the present illustration and othertypes of arrangements with which the present invention can be usedwithout departing from the scope of this invention as defined only by aproper interpretation of the appended claims.

1. A dishwasher having a pre-conditioning steam cycle, the dishwashercomprising: a washing compartment for receiving dishware to be subjectedto a dishwashing program; a wash water assembly for introducing aselected one of wash water and rinse water into the washing compartment,the wash water assembly being controllable to perform at least one of awash/rinse/dry program and a rinse and hold program; a vapor generatorassembly for introducing steam vapor into the washing compartment; and acontrol arrangement for controlling the vapor generator assembly toperform a steam and hold cycle wherein steam vapor is introduced intothe washing compartment at selected intervals.
 2. The dishwasheraccording to claim 1, wherein the control arrangement controls the vaporgenerator assembly to perform a steam and hold cycle in lieu of a rinseand hold cycle.
 3. The dishwasher according to claim 1, wherein thecontrol arrangement controls the vapor generator assembly to perform amodified rinse and hold cycle in coordination with a steam and holdcycle.